Internal combustion engines having a plurality of combustion cylinders are well known. Because of excess heat of combustion, all such engines require some means for cooling of engine components, typically by passage of either atmospheric air or water over engine components.
In air-cooled engines, outer engine surfaces are cooled by the passage of air across the surfaces. The air may be impelled by motion of the engine through the atmosphere, as in a moving motorized vehicle or aircraft, and/or by a supplemental fan.
In water-cooled engines, components such as block and head are jacketed, and cool water is passed through the jacket to remove heat from the components.
The water warmed by such passage is either discharged to the environment and replaced, as in marine vessels, or is circulated through a radiator system which itself is air cooled.
Engine cooling systems typically are sized to meet the thermal demands of engine operation over the full range of engine operating conditions. However, on some occasions an engine cooling system cannot keep up with the thermal demand, usually from lack of adequate coolant flow over the engine surfaces at low engine speeds or vehicle velocities. This problem is well-known, for example, in the field of motorcycle engines.
Certain motorcycles, usually large displacement, air-cooled V-twins, are commonly utilized in parades. However, parade speeds create a problem with these air-cooled engines, as these engines require significant speed-generated air flow across the cooling fins in order to reject the required heat from the combustion process to maintain a comfortable operator environment. Extended operation with negligible mass flow of ambient air across the engine cooling fins results in elevated engine operating temperature, which can be problematic for engine function and durability, as well as for an operator's comfort and safety.
Some motorcycles employ liquid cooling of the engine with a water jacket and remote radiator to facilitate rejection of combustion heat. These radiators also require vehicle speed to generate air flow through the radiator to function as an effective heat exchanger/rejecter. Unless an additional cooling fan is added to create airflow across the radiator, motorcycles with these liquid cooled engines are also susceptible to overheating during extended operation in a parade environment, although perhaps to a lesser degree than air-cooled motorcycles.
An approach to solving this problem in the prior art includes deactivation of the valvetrain of a selected cylinder to prevent further combustion therein. This approach has the effect of preventing generation of additional heat of combustion from the deactivated cylinder or cylinders, but since air in the cylinder is captive, this action does not act further to remove excess heat from the engine, resulting in a rather ineffective strategy for reducing engine over-heat during extended low-rpm, low road speed operation, with significant additional cost, mass, and complexity.
What is needed in the art is a method and apparatus for providing additional air cooling to an internal combustion engine during periods of excessive heat generation.
It is a principal object of the present invention to cool an internal combustion engine at times of low engine load and excessive heat generation.